A writing technique by a magnetic head, which uses a magnetic field generated from a coil, has been used for writing magnetic information in a hard disk drive (HDD) of the prior art. There has been a demand for even higher recording density in HDDs, and it is known that the magnetic field strength, which can be generated by the magnetic head, is reduced due to the influence of demagnetization field components generated at the tip of the magnetic head when the magnetic head is made minute according to the refinement of the recording domains by increasing density. Moreover, when the recording domain becomes minute, a material having a greater magnetic anisotropy is necessary to overcome the thermal instability of the written magnetization direction, so that a greater writing magnetic field is required. Therefore, in a writing technique for high recording density, it is expected that there is a limit for those which use only a magnetic head of the prior art, and a new writing technique is required as an alternative to them.
For instance, a writing technique by a so-called thermal assistance method is proposed. This is a writing technique in which the coercivity is reduced only at the region being written by locally heating the recording medium using a laser beam and by applying a magnetic field. This technique is promising as a magnetic writing technique for high density recording because the writing magnetic field can be reduced. However, since the region to which the laser beam can be focused becomes a heated region, its miniaturization is a problem.
For instance, as a writing technique in which no magnetic field is used, non-patent document 1 proposes a writing technique which uses a spin injection flux reversal. This is a writing technique in which flux reversal is performed by injecting spin-polarized electrons into a magnetic material. However, wiring becomes necessary since the writing current threshold is as high as 106–107 A/cm2 and enough current can not flow without contacting the medium, so that it is not suitable for a writing technique in a non-wiring super high density recording medium such as HDD.
Furthermore, a magnetization control technique using an electric field is proposed as another writing technique. For instance, non-patent document 2 discloses one that tries to control the exchange interaction created between the ferromagnetic materials by controlling the carrier density in the semiconductor layer using an electric field in a lamination structure of ferromagnetic metal/semiconductor/ferromagnetic metal. Moreover, for instance, non-patent document 3 discloses one that tries to control the exchange interaction created between the ferromagnetic materials by providing an insulator layer inside the triple-layered structure of ferromagnetic metal/non-magnetic metal/ferromagnetic metal, such as ferromagnetic metal/non-magnetic metal/insulator layer/ferromagnetic metal, and by applying a voltage between the ferromagnetic metallic layers. Moreover, for instance, patent document 1 discloses one that tries to control the exchange interaction created between the ferromagnetic materials by providing a semiconductor layer outside of the triple-layered structure of ferromagnetic metal/non-magnetic metal/ferromagnetic metal and by controlling the width and height of the Schottky barrier created at the interface between the ferromagnetic metallic layer and the semiconductor by using an electric field. These magnetization control techniques using an electric field make it possible to achieve high density and they are promising as techniques with low power consumption.    [Patent document 1] JP-A No. 196661/2001    [Non-patent documents 1] J. Slonczewski, J. Mag. Mag. Mater. 159, L1 (1996)    [Non-patent documents 2] Mattsonet et al, Phys. Rev. Lett. 71, 185 (1993)    [Non-patent documents 3] Chun-Yoel Youi et al., J. Appl. Phys., 87, 5215 (2000)